练习代码，简单的登陆

import java.util.Scanner;
public class LoginDemo
{
	final String username = "root";
	final String userpassword = "myroot";
	static int sum = 3;
	private static Scanner in = new Scanner(System.in);

	private boolean loginInstructions()
	{
		String inputusername = in.next();
		String inputuserpassword = in.next();
		if(this.username.equals(inputusername) && this.userpassword.equals(inputuserpassword))
		{
			return true;
		}
		sum--;
		return false;
	}

	public static void main(String[] args)
	{
		LoginDemo login = new LoginDemo();
		System.out.println("请输入账号以及密码");
		while(sum <= 3)
		{
			if(sum == 0)
			{
				System.out.println("明天在登陆吧");
				break;
			}
			boolean i = login.loginInstructions();
			if(i)
			{
				System.out.println("登陆成功");
				break;
			}
			System.out.println("登陆失败");
			if(sum >= 1)
			{
				System.out.print("请重新登陆,您还有"+sum+"机会");
			}
		}
	}
}